There has been a lot of recent activtity in the non-invasive study of the cardiovascular system. Traditional methods, such as angiography, usually relied on some invasion into the blood vessels. A disadvantage of invasive techniques is the risk of infection, increased mortality risks and increased morbidity risks. For example, there is a one to five percent mortality rate from angiography. Furthermore, those surviving patients often have traumatic reactions to the injected dye. In particular, increased attention has been focused on obtaining a diagnostic indicator of flow problems throughout the arterial tree. Unfortunately, most methods presently in use have significant detractions. One method recently gaining popularity is the use of ultrasound Doppler velocity meters. This process is described in articles such as the ones by Max Anliker, "Diagnostic Analysis of Arterial Flow Pulses In Man;" Cardiovascular System Dynamics, Beran et al, Eds. (1978) and Gosling and King, "Continuous Wave Ultrasound As An Alternative and Complement To X-rays In Vascular Examinations;" Cardiovascular Applications Of Ultrasound, R. Reneman Ed. (1974). The principal drawbacks in using ultrasound are the complex equipment that is needed, the trained technicians and diagnosticians that are required, the complexity of the procedure and the propensity for error based on incorrect vessel diameter and incorrect relative flow directions, and the inability to use the method as a quick screening test to determine potential problems.
Another approach in the investigation of arterial flow is disclosed in the Findl et al. U.S. Pat. No. 4,166,455. This patent disclosed the theoretical basis for using the electrokinetic phenomenon known as streaming potential to determine reduced flow. That patent, which is incorporated in its entirety herein by reference, discloses a method and a sensor for detecting electrical voltages measured on the skin surface. While that method is satisfactory for locating certain lesions located in arteries near the skin surface, it does not provide a method for overall screening purposes to determine whether there is abnormal flow in the arterial tree.
None of the prior art methods and apparatuses provide a simple, inexpensive screening technique for monitoring the changes in blood flow caused by disease stages, traumatic injuries and other factors. Thus, there is the need for inexpensive, uncomplicated, and easy to use apparatus for rapidly screening individuals to detect problems in the cardiovascular system.